Expert Image Processing Interview Preparation Guide

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Zooming may be viewed as over sampling. It involves the creation of new pixel
locations and the assignment of gray levels to those new locations.

1. 4 connectivity
2. 8 connectivity
3. M connectivity (mixed connectivity)

The need for transform is most of the signals or images are time domain signal (ie) signals can be measured with a function of time. This representation is not always best. For most image processing applications anyone of the mathematical transformation are applied to the signal or images to obtain further information from that signal.

1. RGB model
2. CMY model
3. YIQ model
4. HSI model

d) sampling
Explanation: The sampling points are ordered in the plane and their relation is called a Grid.

c) False Contours
This effect arises when the number brightness levels is lower that which the human eye can distinguish.

Subjective brightness means intensity as preserved by the human visual system.
Brightness adaptation means the human visual system can operate only from scotopic to glare limit. It cannot operate over the range simultaneously. It accomplishes this large variation by changes in its overall intensity.

The number of bits required to store a digital image is
b=M X N X k
When M=N, this equation becomes
b=N^2k

1. RGB model- used for color monitors & color video camera
2. CMY model-used for color printing
3. HIS model--used for color image processing
4. YIQ model-used for color picture transmission

The function textattr in conio.h can be use for this purpose a small program has presented here...

#include<conio.h>
int main()
{
textattr(129);
cprintf("My name is John Smith...");
return 0;
}


here in the textattr till 128 only colors would be set and more than it colors with blink.

Difference between the books is that Digital Image Processing (DIP) deals primarily with the theoretical foundation of digital image processing, while Digital Image Processing Using MATLAB (DIPUM) is a book whose main focus is the use of MATLAB for image processing. The DIPUM book covers essentially the same topics as DIP, but the theoretical treatment is not as detailed. Some instructors prefer to fill in the theoretical details in class in favor of having available a book with a strong emphasis on implementation.

c) Noise
Noise is taken as the Denominator.

The ratio of increment of illumination to background of illumination is called as weber ratio.(ie) ?i/i
If the ratio (?i/i) is small, then small percentage of change in intensity is needed (ie) good brightness adaptation.
If the ratio (?i/i) is large , then large percentage of change in intensity is needed (ie) poor brightness adaptation.

32 gray levels = 25

= 5 bits
256 * 256 * 5 = 327680 bits.

An image can be expanded in terms of a discrete set of basis arrays called basis images. These basis images can be generated by unitary matrices. Alternatively, a given NxN image can be viewed as an N^2×1 vectors. An image transform provides a set of coordinates or basis vectors for vector space.

Image enhancement process is purely dependent on the application where we need to use the enhanced image and the type of degradation in the image. Few solutions from my basic knowledge
1. If image contain so much noises, apply filtering operations such as mean/median etc.
2. If the image is looking too dark or or too bright apply histogram equilization process to improve the contrast.
3. If the image is blurred apply sharpening operations in the image.

b) Interpolation
Interpolation is the basic tool used for zooming, shrinking, rotating, etc.

a) Saturation
Saturation is taken as the Numerator.

Recognition means is a process that assigns a label to an object based on the information provided by its descriptors.Interpretation means assigning meaning to a recognized object.

The region reserved brightness not depend on its intensity but also on its background. All centre square have same intensity. However they appear to the eye to become darker as the background becomes lighter.

Luminance measured in lumens (lm), gives a measure of the amount of energy an observer perceiver from a light source.

Hue is a color attribute that describes a pure color where saturation gives a measure of the degree to which a pure color is diluted by white light.

a) Quantisation
The transition between continuous values of the image function and its digital equivalent is called Quantisation.

b) nearest neighbour interpolation
Bilinear interpolation is where the FOUR neighbouring pixels is used to estimate intensity for a new location.

1. Image Acquisition
2. Storage
3. Processing
4. Display